The oral dosage of vitamin B12 is 25~100μg a day, or 50~200μg every other day, divided into 1~4 times, the specific use of medical advice. Vitamin B12 is converted into methylcobalamin and coenzyme B12 in the body to produce activity. Methylcobalamin is involved in the metabolism of folic acid, and a deficiency of which can lead to megaloblastic anemia. In addition, coenzyme B12 promotes fat metabolism, the human body can cause fatty acid metabolism abnormalities in the absence of coenzyme B12, the clinical symptoms of neurological damage. Vitamin B12 tablets can be used for megaloblastic anemia. Oral, 25 ~ 100 μg a day (1 ~ 4 tablets a day), or every other day 50 ~ 200 μg (every other day 2 ~ 8 tablets), divided into 1 ~ 4 times, or as directed by the doctor. Adverse reactions to vitamin B12 may include hypokalemia and hyperuricemia. Vitamin B12 is contraindicated in persons with known hypersensitivity to vitamin B12. Vitamin B12 for megaloblastic anemia should be checked for potassium 48 hours after initiation. Vitamin B12 deficiency may be accompanied by folic acid deficiency, and folic acid supplementation is recommended for these patients in order to achieve a better therapeutic effect. Vitamin B12 should be used under the guidance of a doctor, and the specific treatment plan should follow the doctor’s instructions in order to better treat the disease. Do not blindly use your own medicine.